Environmental Engineering Reference
In-Depth Information
FIGURE 9.129
Stabilization of a slump slide with anchored premolded concrete panels which conform readily to the shape of
the slope (Itaorna, R.J., Brazil).
Planar slides in mountainous terrain, which usually give warning and develop slowly,
can undergo sudden total failure, involving huge volumes and high velocities with disas-
trous consequences.
Falls, avalanches, and flows often occur suddenly without warning, move with great
velocities, and can have disastrous consequences.
Stability Factors
Slope geometry and geology, weather conditions, and seismic activity are the factors influ-
encing slope stability, but conditions are frequently transient. Erosion, increased seepage
forces, strength deterioration, seismic forces, tectonic activity, as well as human activity, all
undergo changes with time and work to decrease slope stability.
Selection of Slope Treatments
Slope treatments are selected primarily on the basis of judgment and experience, and nor-
mally a combination of methods is chosen.
For
active slides of large dimensions
, consideration should be given chiefly to external and
internal drainage; retaining structures are seldom feasible.
Active slides of small dimensions
can be stabilized by changing their geometry, improving
drainage, and when a permanent solution is desired, containing them by walls. An alter-
native, which is often economically attractive, is to permit the slide to occur and to remove
material continuously from the toe until a stable slope has been achieved naturally. The
risk of total failure, however, must be recognized.
Cut slopes
are first approached by determining the maximum stable slope angle; if too
much excavation is required or if space does not permit a large cut, alternative methods
employing retention are considered. It must be noted that side-hill cuts are potentially far
